EFFECT OF SEED SIZE AND LIGHT REGIME ON SEED GERMINATION AND SEEDLING SURVIVAL IN THREE DOMINANT RAINFOREST TREE SPECIES OF NORTH EAST INDIA

摘要

Seed germination and seedling survival were studied for three dominant tree species viz., Dipterocarpus macrocarpus, Shorea assamica and Mesua ferrea under green house condition. Over all, M. ferrea and D. macrocarpus showed better germination percentage under low light regime (3%) and S. assamica under high (50%) light regime (r2 = 0.58). Seeds of D. macrocarpus and M. ferrea of higher seed mass category showed highest germination percentage, whereas in case of S. assamica, seeds of medium seed massshowed better germination percentage. Seedling survival was not affected by seed mass and light regime in M. ferrea. However, survivality is good for D. macrocarpus in 25% light and least in low light (3%). S. assamica, on the other hand, shows equallygood survival in low and intermediate light regime. Seedling mortality was highest for M. ferrea and S. assamica during winter due to low soil moisture content, whereas in D. macrocarpus, it was the highest during the monsoon, mostly due to pathogenic infection. Large and heavy seeds germinated faster and attained greater germination percentage than smaller seeds. Our result shows that heavier seeds germinate early and their germination percentage is higher than that of the seedlings of smaller seeds. Shading and moisture supplementation increase germination. Production of larger seeds is less advantageous in heavily disturbed areas than in the understorey and all the three species studied can be grown well in moderately disturbed stands rather than inthe highly disturbed ones.